text: var tween = {
    linear: function (t, b, c, d) { //匀速
      return c * t / d + b;
    },
    easeIn: function (t, b, c, d) { //加速曲线
      return c * (t /= d) * t + b;
    },
    easeOut: function (t, b, c, d) { //减速曲线
      return -c * (t /= d) * (t - 2) + b;
    },
    easeBoth: function (t, b, c, d) { //加速减速曲线
      if ((t /= d / 2) < 1) {
        return c / 2 * t * t + b;
      }
      return -c / 2 * ((--t) * (t - 2) - 1) + b;
    },
    easeInStrong: function (t, b, c, d) { //加加速曲线
      return c * (t /= d) * t * t * t + b;
    },
    easeOutStrong: function (t, b, c, d) { //减减速曲线
      return -c * ((t = t / d - 1) * t * t * t - 1) + b;
    },
    easeBothStrong: function (t, b, c, d) { //加加速减减速曲线
      if ((t /= d / 2) < 1) {
        return c / 2 * t * t * t * t + b;
      }
      return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
    },
    elasticIn: function (t, b, c, d, a, p) { //正弦衰减曲线（弹动渐入）
      if (t === 0) {
        return b;
      }
      if ((t /= d) == 1) {
        return b + c;
      }
      if (!p) {
        p = d * 0.3;
      }
      if (!a || a < Math.abs(c)) {
        a = c;
        var s = p / 4;
      } else {
        var s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
    },
    elasticOut: function (t, b, c, d, a, p) { //正弦增强曲线（弹动渐出）
      if (t === 0) {
        return b;
      }
      if ((t /= d) == 1) {
        return b + c;
      }
      if (!p) {
        p = d * 0.3;
      }
      if (!a || a < Math.abs(c)) {
        a = c;
        var s = p / 4;
      } else {
        var s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      return a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b;
    },
    elasticBoth: function (t, b, c, d, a, p) {
      if (t === 0) {
        return b;
      }
      if ((t /= d / 2) == 2) {
        return b + c;
      }
      if (!p) {
        p = d * (0.3 * 1.5);
      }
      if (!a || a < Math.abs(c)) {
        a = c;
        var s = p / 4;
      } else {
        var s = p / (2 * Math.PI) * Math.asin(c / a);
      }
      if (t < 1) {
        return -0.5 * (a * Math.pow(2, 10 * (t -= 1)) *
          Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
      }
      return a * Math.pow(2, -10 * (t -= 1)) *
        Math.sin((t * d - s) * (2 * Math.PI) / p) * 0.5 + c + b;
    },
    backIn: function (t, b, c, d, s) { //回退加速（回退渐入）
      if (typeof s == 'undefined') {
        s = 3.70158;
      }
      return c * (t /= d) * t * ((s + 1) * t - s) + b;
    },
    backOut: function (t, b, c, d, s) {
      if (typeof s == 'undefined') {
        s = 3.70158; //回缩的距离
      }
      return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
    },
    backBoth: function (t, b, c, d, s) {
      if (typeof s == 'undefined') {
        s = 1.70158;
      }
      if ((t /= d / 2) < 1) {
        return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
      }
      return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
    },
    bounceIn: function (t, b, c, d) { //弹球减振（弹球渐出）
      return c - this['bounceOut'](d - t, 0, c, d) + b;
    },
    bounceOut: function (t, b, c, d) {
      if ((t /= d) < (1 / 2.75)) {
        return c * (7.5625 * t * t) + b;
      } else if (t < (2 / 2.75)) {
        return c * (7.5625 * (t -= (1.5 / 2.75)) * t + 0.75) + b;
      } else if (t < (2.5 / 2.75)) {
        return c * (7.5625 * (t -= (2.25 / 2.75)) * t + 0.9375) + b;
      }
      return c * (7.5625 * (t -= (2.625 / 2.75)) * t + 0.984375) + b;
    },
    bounceBoth: function (t, b, c, d) {
      if (t < d / 2) {
        return this['bounceIn'](t * 2, 0, c, d) * 0.5 + b;
      }
      return this['bounceOut'](t * 2 - d, 0, c, d) * 0.5 + c * 0.5 + b;
    }
  };
  